This invention relates to a blade row group.
The aerodynamic loadability and the efficiency of fluid-flow machines, in particular blowers, compressors, turbines, pumps and fans, is limited by the growth and the separation of boundary layers near and on the hub and casing walls. To remedy this problem in the case of high aerodynamic loading and important boundary layer growth on the annulus duct side walls (hub or casing), the state of the art provides solutions only to a limited extent.
State of the art in fluid-flow machines are arrangements with double-row stator wheels, usually employed as exit stator wheels in compressors, or also double-row rotor arrangements in which directly adjacent rotors operate counter-rotatingly, or in which two directly adjacent rotor blade rows are attached to a common drum. A fluid-flow machine of this type is known for example from EP 2 261 463 A2. With these arrangements, and in particular with those having several, directly adjacent blade rows firmly arranged relative to one another (for example several rotor blade rows on the same drum, or several stator vane rows), severe boundary layer separation occurs at higher aerodynamic loading in the boundary zone of the main flow path, i.e. at the hub or casing contour.
The state of the art also includes double-row adjustable stator wheels, the vanes of which at the hub and at the casing are arranged on a rotary base to allow them to be turned in the angle of attack. Due to size restrictions it is usual here to provide a partial radial gap for the rotary base in the circumferential direction, said gap being located along a rear part of the rear profile.
The problems in the edge areas are primarily due to the fact that the favourable arrangement of two adjacent blade edges of a blade row group in the center of the main flow path has an unfavourable effect in the vicinity of the flow path boundary. The required flow deflection may quickly be so high either in parts of the blade height or along the entire blade height that the conventional arrangement leads to very premature separation of the boundary layer flow in the edge areas of the main flow path on the hub and/or the casing walls.